1. Field of the Invention
The present invention relates to an image encoding method and an image encoding apparatus for efficiently reducing and encoding image data, an image decoding method and an image decoding apparatus, and a program.
2. Background Art
Conventionally, as a technique for image compression, international encoding standards, as represented by MPEG (Moving Picture Experts Group), are known. Further, to reduce image data, such a technique is known that improves a compression rate by concurrently using a technique for using an image generated by executing a move searching process between local decoded images in an encoding apparatus as a predicted image or a decoded image, and an existing encoding technique (for example, JP Patent Publication (Kokai) No. 2008-154015 A). More specifically, in JP Patent Publication (Kokai) No. 2008-154015 A, the predicted image generated according to the existing encoding standards, and the image generated by executing the move searching process between the local decoded images are encoded by being switched for every pixel block, and thereby, the compression rate is improved.
However, in the method showed by JP Patent Publication (Kokai) No. 2008-154015 A, that is, the method by which the predicted image generated according to the existing encoding standards, and the image newly generated by executing the move searching process between the decoded images are encoded by being switched for every block, determination information (flag information) on which image is to be used newly becomes necessary in addition to existing flag information. Thus, encoding quantity for the determination information becomes large in some input video image, so that the compression rate when the compression is executed by the method of JP Patent Publication (Kokai) No. 2008-154015 A may become lower than the compression rate when the compression is executed according to the conventional standards.
The present invention is made in consideration of such condition, and provides a technique for improving the compression rate without needing the new determination information.